TITLE: GCN CIRCULAR NUMBER: 30715 SUBJECT: Swift GRB210825.29: Global MASTER-Net observations report DATE: 21/08/25 17:08:40 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs lipunov@xray.sai.msu.ru

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),

D. Buckley (South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),

A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)

MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB210825.29 (trigger No 1070298,15h 55m 20.62s , -54d 04m 12.7s, R=0.05) errorbox 36143 sec after notice time and 36165 sec after trigger time at 2021-08-25 16:56:13 UT, with upper limit up to 16.9 mag. Observations started at twilight. The observations began at zenith distance = 23 deg. The sun altitude is -8.8 deg.

The galactic latitude b = -1 deg., longitude l = 328 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1699842

We obtain a following upper limits.

Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________

36256 | MASTER-SAAO | C | 180 | 16.9 | Filter C is a clear (unfiltred) band.

The observation and reduction will continue. The message may be cited.